IN THE early 1920s, according to ecologists, the British brought trees to Delhi that were native to Mexico and which monopolised sunlight and water — virtually killing any competition from other tree species. More than 90 years later, ecologists and botanists have been working hard to find ways to remove one such tree — vilayati kikar (Prosopis juliflora) — from the Delhi Ridge area, as it has killed almost all other native trees in the forest and wiped out biodiversity. The Ridge area is also known as the ‘lungs of the city’.
In the budget announced this year, the Delhi government for the first time allocated a set amount of Rs 50 lakh for removal of the kikars and replacing them with native species. According to officials in the forest department, they have already written to the Forest Research Institute, Dehradun, to finalise a plan to carry out the massive task.
According to the Delhi government, the Ridge area is spread over an area of 7,777 hectares. Of this, experts at Delhi University said, over 80 per cent land is covered by vilayati kikar.
“The Forest Research Institute is working on a plan which will tell us the methodology we need to adopt to replace these trees, and ensure that the ridge doesn’t look barren. A technical proposal is awaited, based on which the trees will be removed. The experts will tell us how many trees need to be planted to replace each kikar,” a forest department official said.
The forest department also has a working model to take inspiration from. Large swathes in the Aravalli Biodiversity Park in the South Central Ridge area were taken up by the Delhi Development Authority (DDA) for regeneration, and a team headed by renowned ecologist C R Babu went to work on it to bring back native species of Delhi.
“The ecological contribution of Prosopis juliflora is not significant, especially in our context. It is not a big sink for carbon dioxide and it uses a lot of water. It’s roots go down about 22 metres deep, which is much deeper than most other trees. In Tamil Nadu, the High Court ordered the removal of these trees because they deplete the water table,” said Babu, who heads the Centre for Environmental Management of Degraded Ecosystems.
At Aravalli Biodiversity Park, Babu’s team started with heavy pruning of the tree branches so that sunlight reaches the saplings of native trees. The canopy of vilayati kikar is dense and does not let sunlight pass through, scuttling the growth of other trees. “Vilayati kikar requires a lot of sunlight and does not thrive if it is blocked. Once we cleared out the canopy, we planted trees that grow taller than this species. Eventually the native species start to thrive and the kikar trees start to diminish. It is a long-term plan,” Babu said.
Now, there are close to 800 species of trees in Aravalli Biodiversity Park. “When we started, there were about 35 species of birds. Now, there are over 250. The population of jackals has also grown. There were 30 species of butterflies earlier. Now there are105. If a corridor connecting all parts of the Ridge is built, more mammals will return to the forest,” Babu said.